在java中编写布尔语句

Question

我正在做一个要求的练习：

＆＃34;如果一个人年龄介于10到20岁之间，他们可享受50％的折扣＆＃34;

为什么我的布尔语句失败？

package exercises;

import java.util.Scanner;

public class FareDiscountApp {

    public static void main(String[] args) {
        PersonClass discountPerson;

        discountPerson = new PersonClass();

        Scanner keyboard = new Scanner(System.in);

        System.out.println("Please enter the peron's age: ");
        discountPerson.age = keyboard.nextInt();
        System.out.println("Please enter the peron's weight:");
        discountPerson.weight = keyboard.nextDouble();
        System.out.println("Is the person a student (true/false:");
        discountPerson.student = keyboard.nextBoolean();
        System.out.println("Please enter the peron's gender (M/F");
        discountPerson.gender = keyboard.next().charAt(0);

        if (discountPerson.age > 65)
        {
            System.out.println("This peron's bus discount is 100%");
        }
        else if ((discountPerson.student == !(false)) && (discountPerson.age > 10 && < 20))
        {


    }

}

Answer 1

试试这个

else if (discountPerson.student && discountPerson.age > 10 && discountPerson.age < 20)

因为您遗漏了与20

的比较

注意我是如何简化第一次比较并摆脱不必要的括号

Answer 2

没有必要比较布尔值，请在此处查看您的表达式评估的内容：

discountPerson.student == !(false)
=> discountPerson.student == true
=> true == true
=> true

相反，你可以写：

if (discountPerson.student && (discountPerson.age > 10 && discountPerson.age < 20) {
    //...
}

Answer 3

那必须是：

if (discountPerson.student && discountPerson.age > 10 && discountPerson.age < 20) {

    // ...
}